Taste it first,does it taste sweet ? If so then all the sugars haven't turned into alcohol and adding more won't help at this stage. I certainly wouldn't bottle it for fear of fermentation starting again. My King Kegs have an s30 valve in the cap to take the large co2 cylinder (not the co2 bulbs). These s30 valves have a pressure release valve so any excess pressure can be released, a safety valve if you like...
As suggested, have another read up on alternatives via the link given above. I also have had a wherry stuck but the 'stir' has always worked for me so I can't comment on further action. 1020 seems too high to bottle or keg really...